Write the first law of thermodynamics for an isothermal process in an ideal gas.

(N/A) In an isothermal process of an ideal gas,the temperature remains constant.
Since the internal energy $U$ of an ideal gas depends only on its temperature,for an isothermal process,the change in internal energy $\Delta U = 0$.
According to the first law of thermodynamics:
$\Delta Q = \Delta U + \Delta W$
Substituting $\Delta U = 0$ into the equation:
$\Delta Q = \Delta W$
This means that in an isothermal process,the entire amount of heat supplied to the system is used to perform work by the system.